*Purpose: Secondary options for Pneumocystis Jirovecii pneumonia (PJP) prophylaxis in kidney transplant recipients (KTRs) include atovaquone or dapsone. Atovaquone use may be limited by cost/side effects, while dapsone has been associated with hemolytic anemia and methemoglobinemia (MHb). We sought to evaluate hemolytic anemia/MHb complications in KTRs on dapsone PJP prophylaxis at our transplant center.

*Methods: We retrospectively reviewed non-HIV+ KTRs performed from Jan 2008-Dec 2017 at our center who received dapsone 100mg/day for PJP prophylaxis any time after KT. Data collection end date was July 1, 2018. Hemolytic anemia was defined as: any decrease in hemoglobin (Hb) during prophylaxis, plus at least 1 lab finding of hemolysis: elevated LDH or indirect bilirubin, decreased haptoglobin, peripheral smear with burr cells/schistocytes, plus Hb improvement to at least baseline after dapsone discontinued. MHb was defined as: oxygen desaturation/respiratory difficulty by pulse oximetry during prophylaxis, plus MHb level >1.5%, plus symptom resolution after dapsone discontinued.

*Results: Twenty-nine KTRs were included. Mean (SD) age at KT was 53±15 yrs, 34% were male, 34% were black, 41% were deceased donor KTRs, 14% were re-transplants. Median (IQR) time to dapsone initiation was 13 (5-85) days after KT and one KTR was already on dapsone (prior heart transplant). Twenty-six KTRs were taking tacrolimus, mycophenolic acid (MPA), and prednisone, while 3 had MPA held for leukopenia. Glucose-6-phosphate dehydrogenase (G6PD) screening was performed in 90% of KTRs and all results were normal. Reasons for dapsone use were: 15 (52%) had atovaquone cost/taste issues, 7 (24%) had sulfamethoxazole-trimethoprim (SMX-TMP) allergy documented, 5 (17%) had SMX-TMP intolerance (e.g. hyperkalemia, leukopenia, thrombocytopenia), and 2 (7%) were unknown from chart review. One (3%) KTR with normal G6PD was diagnosed with hemolytic anemia within 1 mo of dapsone initiation while erroneously taking dapsone 3 times/day. Hb dropped 3.8 gm/dL over 19 days and required blood transfusion. One (3%) KTR with normal G6PD had suspected hemolytic anemia within 1 mo of dapsone initiation (0.8 gm/dL Hb drop over 9 days), but other labs to confirm diagnosis were unavailable. One (3%) KTR with normal G6PD was diagnosed with MHb (MHb level 9.6%) 4 mos after dapsone initiation, while also presenting with viral bronchitis.

*Conclusions: KTRs on dapsone prophylaxis should be monitored for hemolytic anemia/MHb even if G6PD results are normal. Diagnosis of these complications should be confirmed by laboratory testing, as anemia can have other etiologies in KTRs. Allergy/intolerance to SMX-TMP should be further evaluated to avoid unnecessary use of secondary PJP prophylaxis.

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